1. Field of the Invention
The present invention relates to inkjet recording systems and recording apparatuses having excellent initial ink chargeability.
2. Description of Related Art
Recent outstanding improvement in inkjet recording technique has enabled production of high-definition images which are very similar to photographs. Consequently, inkjet recording has been widely used in various fields of art. In association with this, there is a need of improving printing speed as well as obtaining high-definition images. As a measure for improving printing speed, there is known a method of increasing the number of nozzles, and discharging ink droplet in larger amount per unit time from each head. In such a measure, driving frequency of 15 kHz or higher is desired, and it is necessary to supply ink that is to be used in unit time by every head without any excess and deficiency from an ink cartridge.
However, in the initial of ink to the inkjet head, the pressure to each nozzle is not equally distributed since there are a great number of nozzles, whereby bubbles remain in the ink flow channel and discharge defect and continuous discharging property are affected. Such bubbles strongly attach to the inner wall surface of the channel, and cannot be easily discharged.
In order to overcome such a problem, a method of imparting hydrophilicity by acid treatment or plasma treatment, or of containing a filler imparted with hydrophilicity by acid treatment has been proposed (e.g., Japanese Patent No. 3454514 publication) to improve the wettability of a head constituting member made of a resin material. In terms of increasing the toughness and strength of the piezoelectric element, a method of forming each layer by burning in a laminate-type piezoelectric element so as to increase the toughness has been proposed (see e.g., Japanese Patent Application Laid-Open Publication No. 2004-114308).
However, in the structure disclosed in the Japanese Patent No. 3454514 publication in which ink directly contacts piezoelectric elements, piezoelectric elements may get corroded or deteriorated by hydrophilizing treatment. Moreover, since the piezoelectric element disclosed in the Japanese Patent Application Laid-Open Publication No. 2004-114308 is a burnt member of ceramics or the like, its surface has fine bumpy structure, so that ink is difficult to be charged. When bubbles remain on the surface of the piezoelectric element that generates pressure due to failure in charging of ink, the generated pressure will not travel satisfactorily, so that discharge defects such as lowering in continuous discharging property, decrease in discharging speed, or discharge failure will occur.